Untitled Document

Physics Demo Number: 119

Approximate

Run Time: 5 min

Longitudinal Waves with Help of Center-Pivoted , Spring-Coupled Rods

Demo Description

A set of vertical steel rods , each of which is pinned at its center, L/2, and having spring couplings between each adjacent pair of rods at about their L/4 and 3L/4 points is used as a graphic simulation of longitudinal wave motion. This mechanical model can aid in explaining how to excite longitudinal pulses and waves.

Scientific Principles

Particles vibrate back and forth in the direction of energy flow in longitudinal waves.

Equipment

Pasco Apparatus
Black Light

Equipment Location

[E-1-1]-[E-2-1]
[C-2-5]

Instructions

The Pasco apparatus for demonstrating the concept of longitudinal waves is pictured in the first photo. The apparatus lives on the second shelf of [G-1] and [G-2] columns.

One may illuminate the greenish dots on the rod heads, seen in the next photo, with the Black-Light from [C-2-5] to cause them to fluoresce for added visual effect.

The third photo shows the new (Sept 2011) shop-made longitudinal wave demonstrator with clumps of green disks. It lives on [A-2-2].
These clumps are coupled by the interactions of magnets ( similar to the one in the last photo) sliding on a carbon rod through their centers.
The plastic disks are press fitted over the OD's of the magnets.
There is with a hand rotator for feeding energy into the line of disk clumps.